Cartilage

• Diagnostic Characteristics: Large round cells, avascular, perichondrium, lots of amorphous extracellular matrix
• Active secretion of sulfated molecules so staining in extracellular matrix is darker
  • Aggrecan Aggregates made from keratin and chrondriotin
• Two types of growth:
  • Interstitial Growth
    • Clumping chondroblasts in isogenous groups within the cartilage
    • May not see many fibers because cells are still growing
  • Appositional Growth
    • Two layers in perichondrium: fibrous layer and chondrogenic layer
      • Appositional growth of cartilage occurs in chondrogenic layer
• No wandering or plasma cells

Elastic Tissue

• Has perichondrium, avascular, large round cells, lots of extracellular matrix
• Elastic fibers stain darkly, with fibers splitting in acute angles

Fibrocartilage

• Two components of intervertebral disk:
  • Anulus fibrosis
    • Made of fibrocartilage – Collagen Type I
  • Nucleus pulposis – Gelatinous matrix
• For shock absorption

Compact Bone

• Dried specimen have osteocytes removed, leaving holes that have been filled with India ink.
  • Holes are the remaining lacunae
• Canaliculi can be seen reaching towards the next cell
  • Inside are cellular processes of the osteocyte
• Limits of individual osteons can be distinguished, and interstitial lamellae
  • Interstitial lamellae are remnants of former osteons and have incomplete parts of Haversian systems
  • Haversian canals are lined by bone lining cells
• Volkmann’s canal appears like a dumbbell shaped structure without concentric rings of osteocytes
  • Volkmann’s canal runs perpendicularly to bone surface
  • Do not want Volkmann’s canal to run entire length of a bone because if the bone breaks, the indirect damage would kill all the cells in the bone when nutrient supplies are cut
• Internal remodeling can be observed through osteoclast action
  • Resorbption canal can be found by looking for big holes the size of an osteon without concentric rings
  • Forming osteons look like a hole larger than central canal with a few concentric rings
• Oldest osteocyte is nearest to the cement line